Specific objectives and methods are presented as a means towards defining the primary mechanism of lead's action at the system, cellular and subcellular levels. The program measures the subtle changes that occur when cells are exposed to lead to determine if the seemingly casual nature of lead on microorganisms is manifested in numerous events of "minor" chemical alterations, the total of which would be biologically significant but usually unidentified. Proposed studies are designed to evaluate the physical chemical properties of the cytosol and membranal ribosomal contents of bacteria and the eukaryotic organisms Acanthamoeba and chlamydomonas exposed to lead to further test the effectiveness of lead in the alteration of the ribosome particles of cells; to determine the effectiveness of the outer-membrane of gram-negative bacteria for lead binding properties in comparison to the role of lead-immobilization in cytoplasmic membranes of gram-positive bacteria; to determine if the outer membrane is a feature in gram-negative bacteria that protects against specific toxic elements and inciting agents; to establish the effectiveness of lead to induce morphological convertant as was observed in preliminary studies; to evaluate the virulence and serological properties of exotoxins and bacteria cultivated in media containing lead salts; to search for cell free components that may be involved in the solubilization and transport of insoluble lead salts; and to conduct a pilot study on the effects of lead on nitrogen-fixing bacteria, emphasizing their infectivity potential into nodules and nitrogen fixation potentials. Through these programs of study we intend to accumulate basic data for reference sources on the basic action of lead on biological systems and to provide information on the impact of lead on the microbial world.